1. Field of the Invention
The invention relates to a movable-window safety device for detecting the presence of an obstruction in an opening closable by a power-driven window glass, comprising resilient material forming a resilient channel for mounting in a rigid window frame and for receiving an edge of the moving window glass when so mounted, the resilient channel being dimensioned so that its two side walls have extensions beyond the rigid window frame whereby an obstruction entering the window opening from either side thereof is moved into contact with a respective one of the extensions by the moving window glass and applies a force through the extension to the respective side wall and directed towards the base of the resilient channel, electrical detecting means mounted within and extending along the rigid window frame so as to be acted on by the said force and to produce a corresponding electrical signal, the width of the electrical detecting means extending substantially across the width of the resilient channel so as to respond to the said force applied through either of the extensions, and control means responsive to the electrical signal to arrest power-driven movement of the window glass.
2. Description of the Related Art
One such device is shown in FR-A-1 549 640 (corresponding to GB-A-1 98 439). In one form of this known device, the resilient channel is mounted within an additional rigid channel made of electrically conductive material. The combination of this rigid channel and the resilient channel is mounted within the rigid window frame by means of rubber buffers which allow the combination to be moved against the resilience of the rubber buffers by the force produced by an obstruction so that the rigid channel moves into contact with another conductor also resiliently supported from the window frame. Such an arrangement comprises a multitude of separate parts and, accordingly, its assembly would be difficult. In another form of this known device, the outside of the base of the resilient channel carries an electrical conductor which is moved by the force caused by an obstruction into contact with the rigid window frame. In this case, the conductor cannot be completely sealed from the surrounding air because the resilient channel must be sufficiently free to slide within the rigid window frame.
EP-A-0 648 628 describes movable-window safety devices in which a conductor forming one plate of a capacitor in an electrical oscillating circuit is embedded in part of a window channel, or a part associated with a window channel, so as to detect the presence of an obstruction in the window opening by non-contact means--the obstruction altering the frequency of the oscillator. However, with such non-contact methods it is difficult to ensure reliable operation over a long period of time and in a variety of different ambient conditions. In another form described, the conductor is embedded in a lip extending externally from a window channel so as to be physically moved by direct contact between the lip and an obstruction on one side of the window opening. However, such an arrangement is not effective in detecting obstructions approaching from either side of the window opening.